Electric arc welding is well known, and is performed with a variety of processes using a variety of types of equipment. One electric arc welding process is a pulse spray process, which is typically performed using a wire feeder and a power supply. An example of a prior art power supply used in pulse spray welding is a Miller S64M™ wire feeder. The Miller S64M™ wire feeder may be used with a Miller XMT304™ power supply.
Typically, in pulse spray processes, power is provided from the power supply to the wire feeder, and the wire feeder provides the wire and power to the arc. The wire feeder typically includes a controller, which may be part of or separate from the wire feeder, and which controls the wire feed speed based on a user-selected input. Additionally, the controller provides a command signal to the power supply which causes the power supply to output a current and voltage at a desired magnitude. The command is produced at least in response to a user-selected wire feed speed. The current amplitude is often controlled as a function of time, switching between a background current and a peak current, thus creating a pulsed output.
The welding process is often controlled by controlling various welding parameters. For example, the pulse spray process is typically controlled by controlling such welding parameters as peak amps, background amps, pulse width, voltage, ramps, and frequency. The parameters are typically controlled using a controller which provides control signals to the wire feeder (or power supply). Some welding power supplies control the ramp up and ramp down (transition from background to peak, or peak to background). Also some welding power supplies provide an adaptive output voltage where the voltage is controlled to provide a desired or constant arc length. As used herein, welding parameters refer to parameters of the welding power output, such as peak amps, background amps, frequency, pulse width, voltage (constant or adaptive) ramp up, and ramp down. Adaptive voltage, or adaptive arc length, as used herein includes adjusting (changing or scaling) an output parameter, pulse frequency modulation for example, to maintain a constant or desired arc length. Because these welding parameters are used to control the output it may be said that the output is characterized by a plurality of output parameters.
Some wire feeder controllers include factory programs which preset various welding parameters. The values for these parameters are stored by the controller (often in digital or other types of memory). Also, many controllers allow the user to store user-created programs which store user-selected welding parameters. In such a case, the user teaches or sets the desired values for welding parameters, and stores them in the memory.
When the user wishes to access either the factory preset or the user-created programs, they are individually selected using some type of digital interface. Then, the controller commands the power supply to provide power at the called for current, peak current, background current, frequency, ramps and pulse width, thus providing the desired welding parameters.
Different types of welding require different types of arc characteristics (such as the plasma cone angle\width and intensity, hereafter referred to as arc width). For example, flat, horizontal down, welding typically may be performed using a relatively wide arc. Conversely, overhead welding, or welding in other difficult or inconvenient physical positions, often requires a narrow arc.
The preset factory programs are typically set to provide for welding with a wide arc, since this is the one most inexperienced welders will use. To access the narrower arc the welder must adjust the welding parameters manually and individually until the desired arc is obtained. It may be necessary to decrease one parameter as another parameter is increased, without changing other arc characteristics. Without changing other arc characteristics, as used herein, refers to not changing an arc characteristic from the standpoint of the user and/or in such a way the arc is adversely affected, such as not changing arc length to the extent the weld is adversely affected or the user notices the change.
However, many welders lack the experience to know how to properly adjust the various parameters, and in particular welders do not understand the interaction between adjusting various parameters. For example, to decrease arc width, frequency is increased. However, increasing frequency also increases arc length. Many welders do not know this, nor do they know how to adjust the other welding parameters to offset the effect of changing frequency on arc length.
Some prior art systems provide for the user to automatically adjust arc width. As described in U.S. Pat. No. 6,121,575 (owned by the assignee of the present invention), the system adjusts welding parameters with a single knob (i.e. a single arc control input) that controls arc width (or a different arc characteristic) without adversely affecting some other arc characteristics. Specifically, the arc width adjustment is made by adjusting three or four welding parameters simultaneously, such that one or more other characteristics of the arc are minimally affected. Simultaneous, in this context, means at the same time from the standpoint of the user and the welding process. They might occur one after the other, but so far as the user observes by watching the welding process, they occur at the same time.
A single digital knob (or other input device such as a digital input panel, keyboard, analog knob, sliding switch, etc) on the controller allows the user to select between an arc width adjustment of 0 and 20. An arc width adjustment of 0 is no arc width adjustment, and an arc width adjustment of 20 is the maximum arc width adjustment (narrow arc cone) in the preferred embodiment. No adjustment is having the parameters be as they were in the original program, which is typically best for flat, horizontal down, welding (i.e., using a wide arc).
While the system described in U.S. Pat. No. 6,121,575 is a considerable advance over the prior art, it only controls three or four parameters, and does not control adaptive arc length (output voltage) in response to the arc width setting. Thus, when changing arc width the arc length other characteristics may remain constant in some circumstances, but under other circumstances changing the arc width will also change the arc length. Also, that system provided two gains, one for over wire feed speeds of more than 225 IPM, and one for less than 225 IPM. This caused a step change from above and below 225 IPM, which was noticeable at the arc.
Accordingly, it is desirable that a welding power supply and wire feeder include a controller that allows the user to adjust the arc width using a single knob, such that more five or more welding parameters, preferably including arc voltage, are adjusted to obtain a desired arc width, while maintaining one or more other characteristics of the arc, preferably including arc length.